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Product
Dissection
An Engineer's-Eye View of Your Toaster
Technology touches today's teens, from
their compact disc players to their hair
dryers and pocket calculators. Rarely,
though, do they consider how machines
and technology-and the engineering that
makes them possible-affect their lives.
Age Level: 11-18 years
Objectives
The overall objectives of this exercise are to allow
the students to see first-hand the:
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Connections between science and engineering.
•
Impact that engineers (the creators) have on
the lives of people (the customers/users).
Engineering is done for people.
•
Engineering is a team effort.
Overview of Exercise
This exercise, done in teams of two or three
students, is designed to give students an
opportunity to take a machine or device apart; this
is referred to as "dissection". We often take for
granted how machines affect our lives, and seldom
consider the inner workings of these devices. We
also fail to acknowledge the engineers who
designed and built them.
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Materials
On a per team basis (teams are comprised of two or
three students):
• Machine or device for each team (see notes
below)
• Disassembly kit (tools needed for taking the
device apart, any written instructions necessary
for disassembly plus several sheets of paper for
note taking); 1 per team. The specifics of the kit
will depend upon the device that you choose to
use, but keep the tool set simple (e.g., a single
screw driver).
• Large piece of butcher paper (optional)
Assistants. While the exercise can be run effectively
with a single instructor, it makes the entire experience
much more personal if there are a number of
assistants (sometimes referred to as coaches) who
can aid the student teams through the disassembly
stage. Assistants can be the regular classroom
teacher, undergraduate/graduate engineering college
students, and/or other practicing engineers. You and
your assistants will want to become thoroughly
familiar with the device to be dissected as well as
general administration of the exercise in advance of
the class session. Using assistants will help give
students a broader picture of "what engineers look
like", so if possible strive for diversity in your assistant
pool; you might also consider selecting assistants
who represent different engineering disciplines. For a
class of 30 students, two assistants plus the
instructing engineer work well. Recommended
prerequisites for device selection are that it:
• Can be taken apart with simple tools (e.g.,
screwdrivers, snap fits).
• Is of a size that two or three students can work
around and on it (not so small that one needs a
magnifying glass to see, or so large and heavy
that it is difficult to move and hold).
• Has a number (e.g., at least 4, but not more than
30) of mechanical components (e.g., springs,
gears, bearings) inside.
• Has an electrical aspect to it (e.g., it is battery
powered). This prerequisite is desirable but not
necessary.
• Costs less than $10/device. The reasons for this
are twofold: to keep overall cost of the exercise
down and to allow students to see the amount of
engineering involved even in relatively
inexpensive devices works. A very important part
of the exercise is for the teams to see how the
external function of the device is achieved
internally. Does not require detailed disassembly
instructions.
Items that typically cost less than $5 each:
Wind-up toy (e.g., cars, animals)
VCR tape (to be compared with a cassette tape)
Shaver (e.g., a variety of disposable shavers)
Ball point pen
Electrical outlet
Stapler
Disposable camera
Mechanical pencil
Electrical switch
Flashlight
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Other suggested devices/machines:
Clock
Power drill
Electric toothbrush
Hair dryer
Smoke detector
Timer
Manual drill
Food scale
Tape recorder
Fishing reel
Electric razor
Bathroom scale
Pencil sharpener
Jack (e.g., car)
Toaster
Telephone
Lawn sprinkler
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Now for your class visit.
1. Introduce yourself and any assistants working
with you to the class. As part of this introduction
mention briefly any products with which you have
been involved as an engineer. This should take
no more than five minutes.
2. Ask the group to generate a list of all of the
machines that they have touched today. Write the
list on the blackboard or the butcher paper-or
better yet, have a student list the items. The basic
idea is to get the students to start recognizing that
engineered products are a part of their every
lives. This should take no more than 5 minutes.
Where to find devices (and other ideas):
• Hardware stores
• Target stores
• Surplus or outdated equipment manufactured
by your employer
• Drugstores
• Toy stores (e.g. Toys 'R Us)
• K-Mart
• Salvage yard
Lesson Outline
Prior to your session with the students, you need to
become the "expert" with the device. Take it apart and
put it back together enough times so that you have a
good feel for the difficulties involved. If there is some
aspect of the disassembly or reassembly that is
particularly tricky, consider creating a simple handout
on the procedure. In addition, go over the exercise
with your assistants and with the regular classroom
teacher. Discussing the exercise with the teacher will
help you:
3. Divide the class into teams of two or three
students per team.
4. Distribute the products to be dissected and
associated kits, one per team. Selecting a device
to be explored by the teams is where the bulk of
your preparation will be spent. It is recommended
that all teams be working on the same type of
product/device: (e.g., wind-up toy), but you could
have half of the team dissecting one
brand/design, and the other half a different
brand/design.
5. Have the student teams take about five minutes
to "play" with their device (e.g., push buttons, turn
it on) and write down the answers to the following
questions:
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What does the device do?
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How many parts are inside?
•
What science/scientific principles were used in
this machine?
•
How many engineers do you think were involved
in making this machine'? What types of engineers
are involved?
6.
Have the teams, spend no more than 20 to 25
minutes taking the device apart AND putting it
back together. The associated kit should contain
the tools necessary to disassemble the device
(e.g., screwdriver, magnet for collecting screws).
Warn the teams when their work period is half
over so that they can start reassembly. Their
explorations should aid them in answering
•
What does the device do and how does it do it?
(Especially encourage sketching in answering
this question).
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How many parts are inside?
1. Determine likely questions.
2. Learn the class size and determine the number of
teams.
3. Decide how to divide the class into groups. (A
really organized teacher might have the class
already arranged in their groups when you arrive.
This might be particularly important to ensure that
well-balanced teams are formed; the teacher
knows her/his students best).
4. Become familiar with the curriculum (e.g., it would
be terrific if the teacher could discuss pertinent
science principles in advance of the dissection
exercise so that when the engineer arrives and
asks what science or scientific principles were
used in the device, the teacher has already
introduced some of those principles).
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• What science/scientific principles were used in this
machine (e.g. chemistry in batteries and
materials, physics in electromagnetism and load
transfer, biology in human factors)?
career decisions are a bit more remote for this age);
you might also talk with the classroom teacher
beforehand concerning the level of career readiness
of the students.
• How many engineers do you think were involved in
making this machine? What types of engineers
were involved?
Suggested Reading
• What other machines would you expect to find
similar components in?
The Way Things Work
by David Macaulay Houghton Mifflin Company, 1988.
• How do you think it was assembled? How much do
you think it cost to build?
How Things Work
by the Editors of Consumers Guide,
Publishers International, 1990.
Remind the students that they are responsible for
disassembling and reassembling the device as well
as answering the questions (in words or sketches).
This activity provided by
As the student teams are disassembling you and your
assistants should wander among the groups, lending
suggestions when they seem to be having a difficult
time understanding a particular aspect of the device,
or asking them probing questions about what they are
seeing. Do not assume that all of the students have
been taking things apart since they were little and
know even which way to turn the screwdriver to
remove a threaded fastener.
7. Have everyone stop working and have one
member of each team orally present the team’s
answers; record the answers on the blackboard or
butcher paper. Butcher paper is nice in that it
leaves the classroom with an artifact of the
experience.
You might have the first group report on Question
#1 and then have the second group answer
Question #2-adding any details to the answer for
Question #1, etc. When talking about the types of
engineers involved in creating the device, be sure
the list reflects the breadth of the engineering
profession (e.g., materials engineers, industrial
engineers, environmental engineers, etc.).
Extensions
You could leave the devices in the classroom for
further exploration and/or complete reassembly. Also
suggest other devices/ machines that students might
like to take apart, and where they might find
inexpensive examples (e.g., secondhand stores,
garage sales). They could even "play doctor" with
machines that no longer function in terms of
diagnosing what is wrong. All ages like the idea of
"sanctioned" disassembly. With middle school
students you may want to focus more on the science
integral to the device than the specific roles that
engineers played in its creation (if only because
The Synthesis Engineering Education Coalition, Funded by the National
Science Foundation, the coalition is charged with the task of reshaping
undergraduate engineering education while increasing the participation
those currently underrepresented in technical disciplines. Member
universities include Cal Poly-San Luis Obispo, Cornell, Hampton, Iowa
State, Southern, Stanford, Tuskegee, and the University of California at
Berkeley. (For more information about this exercise, contact Dr. Sheri
Sheppard in the Design Division of the Mechanical Engineering Department
at Stanford University, 415-725-1590 or shepppard@sunrise.stanford.edu)